1. Field of the Invention
This invention relates to a portable telephone, and more particularly, to a portable telephone which detects, with a simple structure, hook conditions when it is mounted on an on-vehicle adapter or on-vehicle holder.
2. Description of the Related Art
There is provided inside a vehicle, an on-vehicle adapter or on-vehicle holder for a portable telephone for connecting the portable telephone to an external antenna. When the portable telephone is laid to be mounted on the on-vehicle adapter, an external antenna connector provided on a back face of the portable telephone comes into contact with an external antenna connector of the on-vehicle adapter. This connector is connected to the external antenna provided on the vehicle, and the portable telephone waits for a telephone communication through the external antenna.
When this portable telephone is lifted from the on-vehicle adapter, the portable telephone will be in an off-hook condition and thus a required communication will start. When the portable telephone is placed on the on-vehicle adapter, it will be in an on-hook condition to terminate the telephone communication. In order to detect the hook conditions of this portable telephone, a reed switch is incorporated in a conventional portable telephone, while a magnet is provided on the on-vehicle adapter or on-vehicle holder. The hook conditions are discriminated according to whether or not the reed switch on the portable telephone detects a magnetic field of this magnet, and operations according to the respective hook conditions are conducted.
However, as the portable telephone becomes more and more compact, an area for installation inside the portable telephone is limited. With respect to the hook detecting method by means of a combination with the on-vehicle appliances, which is less frequently used among the forms in which the portable telephone is used, a method for conducting such detection without the reed switch has been sought for.
The present invention is to comply with such requirements and it is an object of the present invention to provide a portable telephone which can detect, with a simple structure, the on-hook condition and the off-hook condition when combined with the on-vehicle appliances.
According to the present invention, the hook conditions are detected by utilizing the shield portion of the external antenna connector portion of the portable telephone.
When the portable telephone is mounted on the on-vehicle adapter or on-vehicle holder, the external antenna connectors respectively on the portable telephone and the on-vehicle adapter or the like are connected with each other so that their shield portions also are connected with each other. By making a part of the shield portion of the portable telephone as a detecting terminal, and by monitoring a voltage level at the detecting terminal, the connection between both the shield portions is discriminated. Recognizing the connected state of the shield portions as the on-hook condition, while recognizing the unconnected state of the shield portions as the off-hook condition, the hook conditions are detected.
According to a first aspect of the present invention, there is provided a portable telephone comprising an external antenna connector portion for connecting it to an external antenna, wherein hook conditions are detected by utilization of the external antenna connector portion. In the on-hook condition where the portable telephone is mounted on the on-vehicle adapter and the like, the shield portions provided on both the portable telephone and the on-vehicle adapter contact with each other. On the other hand, in the off-hook condition where the portable telephone is disengaged from the on-vehicle adapter or on-vehicle holder, there is no contact between the shield portions. By detecting this change in condition, it is possible to detect the hook conditions.
According to a second aspect of the present invention, there is provided a portable telephone, wherein a portable telephone is provided with a detecting terminal formed by utilization of a part of the shield portion, the detecting terminal being earthed when the portable telephone is mounted on an on-vehicle adapter or on-vehicle holder, the detecting terminal becoming open when the portable telephone is disengaged from the on-vehicle adapter or on-vehicle holder. When the portable telephone is mounted on the on-vehicle adapter or the like, the detecting terminal formed of a part of the shield portion will be in communication with the other part of the shield portion to reach the same electric potential (grounded electric potential). When the portable telephone is disengaged from the on-vehicle adapter or the like, there will be no contact between the shield portions, resulting in an open state of the detecting terminal. A voltage level of the detecting terminal is monitored by means of a voltage detector in a microcomputer or the like, whereby the hook conditions can be judged.